报错现象 今天给客户一个单实例环境配置监听，创建正常，查询状态异常报错 tns 12541 tns 12560 tns 00511 linux error 111:connection refused 匹配MOS Starting TNS Listener or LSNRCTL Start Yields TNS-12541, Linux Error: 111: Connection Refused (文档 ID 343295.1) >lsnrctl status Any of the following listener error stacks might be thrown: Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=<hostname>)(PORT=1521))) TNS-12541: TNS:no listener TNS-12560: TNS:protocol adapter error TNS-00511: No listener Linux Error: 111: Connection refused Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC))) TNS-12537: TNS:connection closed TNS-12560: TNS:protocol adapter error TNS-00507: Connection closed Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=<hostname>)(PORT=1521))) TNS-12547: TNS:lost contact TNS-12560: TNS:protocol adapter error TNS-00517: Lost contact Linux Error: 104: Connection reset by peer CHANGES This is likely a new installation. CAUSE 1. There is possibly an incorrect IP Address specified for the host in the /etc/hosts file. For example: 192.xxx.yyy.zzz <hostname>.<domain name> Whereas the actual ip address for the host "<hostname>.<domain name>" is 192.aaa.bbb.ccc 2. Also, the localhost reference may be incorrect or missing from the /etc/hosts file. 3. Oracle may not have read access to /etc/nsswitch.conf file. SOLUTION To implement the solution, please execute the following steps: 1. Correct the mapping in the /etc/hosts file by adding/correcting the IP address and/or hostname reference for the Unix/Linux Server (both long and short host names). For example: # Add or edit the /etc/hosts file to include a valid entry for the Server: 192.aaa.bbb.ccc <hostname>.<domain name> <hostname> 2. Check that the localhost loopback name and address are correct (both long and short host names). An example of a correct localhost entry would be as follows: 127.0.0.1 localhost.localdomain localhost 3. Remember to save the /etc/hosts file and then start the listener. 本次是配置/etc/hosts文件时，未注意直接清空/etc/hosts文件导致Localhost信息丢失，最终导致监听程序无法正常运行 4. Check permissions on /etc/nsswitch.conf file to ensure group and other have read access. - If necessary change permisions on /etc/nsswitch.conf as follows: chmod 644 /etc/nsswitch.conf